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Small molecule structure correctors abolish detrimental effects of apolipoprotein E4 in cultured neurons.

ABSTRACT: Apolipoprotein E4 (apoE4), the major genetic risk factor for late onset Alzheimer disease, assumes a pathological conformation, intramolecular domain interaction. ApoE4 domain interaction mediates the detrimental effects of apoE4, including decreased mitochondrial cytochrome c oxidase subunit 1 levels, reduced mitochondrial motility, and reduced neurite outgrowth in vitro. Mutant apoE4 (apoE4-R61T) lacks domain interaction, behaves like apoE3, and does not cause detrimental effects. To identify small molecules that inhibit domain interaction (i.e. structure correctors) and reverse the apoE4 detrimental effects, we established a high throughput cell-based FRET primary assay that determines apoE4 domain interaction and secondary cell- and function-based assays. Screening a ChemBridge library with the FRET assay identified CB9032258 (a phthalazinone derivative), which inhibits domain interaction in neuronal cells. In secondary functional assays, CB9032258 restored mitochondrial cytochrome c oxidase subunit 1 levels and rescued impairments of mitochondrial motility and neurite outgrowth in apoE4-expressing neuronal cells. These benefits were apoE4-specific and dose-dependent. Modifying CB9032258 yielded well defined structure-activity relationships and more active compounds with enhanced potencies in the FRET assay (IC(50) of 23 and 116 nm, respectively). These compounds efficiently restored functional activities of apoE4-expressing cells in secondary assays. An EPR binding assay showed that the apoE4 structure correction resulted from direct interaction of a phthalazinone. With these data, a six-feature pharmacophore model was constructed for future drug design. Our results serve as a proof of concept that pharmacological intervention with apoE4 structure correctors negates apoE4 detrimental effects in neuronal cells and could be further developed as an Alzheimer disease therapeutic.

SUBMITTER: Chen HK

PROVIDER: S-EPMC3285306 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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Small molecule structure correctors abolish detrimental effects of apolipoprotein E4 in cultured neurons.

Chen Hung-Kai HK Liu Zhaoping Z Meyer-Franke Anke A Brodbeck Jens J Miranda Rene D RD McGuire James G JG Pleiss Michael A MA Ji Zhong-Sheng ZS Balestra Maureen E ME Walker David W DW Xu Qin Q Jeong Dah-eun DE Budamagunta Madhu S MS Voss John C JC Freedman Stephen B SB Weisgraber Karl H KH Huang Yadong Y Mahley Robert W RW

The Journal of biological chemistry 20111212 8

Apolipoprotein E4 (apoE4), the major genetic risk factor for late onset Alzheimer disease, assumes a pathological conformation, intramolecular domain interaction. ApoE4 domain interaction mediates the detrimental effects of apoE4, including decreased mitochondrial cytochrome c oxidase subunit 1 levels, reduced mitochondrial motility, and reduced neurite outgrowth in vitro. Mutant apoE4 (apoE4-R61T) lacks domain interaction, behaves like apoE3, and does not cause detrimental effects. To identify ...[more]

PMID: 22158868

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Project description:The APOE gene is diversified by three alleles ε2, ε3, and ε4 encoding corresponding apolipoprotein (apo) E isoforms. Possession of the ε4 allele is signified by increased risks of age-related cognitive decline, Alzheimer's disease (AD), and the rate of AD dementia progression. ApoE is secreted by astrocytes as high-density lipoprotein-like particles and these are internalized by neurons upon binding to neuron-expressed apoE receptors. ApoE isoforms differentially engage neuronal plasticity through poorly understood mechanisms. We examined here the effects of native apoE lipoproteins produced by immortalized astrocytes homozygous for ε2, ε3, and ε4 alleles on the maturation and the transcriptomic profile of primary hippocampal neurons. Control neurons were grown in the presence of conditioned media from Apoe -/- astrocytes. ApoE2 and apoE3 significantly increase the dendritic arbor branching, the combined neurite length, and the total arbor surface of the hippocampal neurons, while apoE4 fails to produce similar effects and even significantly reduces the combined neurite length compared to the control. ApoE lipoproteins show no systemic effect on dendritic spine density, yet apoE2 and apoE3 increase the mature spines fraction, while apoE4 increases the immature spine fraction. This is associated with opposing effects of apoE2 or apoE3 and apoE4 on the expression of NR1 NMDA receptor subunit and PSD95. There are 1,062 genes differentially expressed across neurons cultured in the presence of apoE lipoproteins compared to the control. KEGG enrichment and gene ontology analyses show apoE2 and apoE3 commonly activate expression of genes involved in neurite branching, and synaptic signaling. In contrast, apoE4 cultured neurons show upregulation of genes related to the glycolipid metabolism, which are involved in dendritic spine turnover, and those which are usually silent in neurons and are related to cell cycle and DNA repair. In conclusion, our work reveals that lipoprotein particles comprised of various apoE isoforms differentially regulate various neuronal arbor characteristics through interaction with neuronal transcriptome. ApoE4 produces a functionally distinct transcriptomic profile, which is associated with attenuated neuronal development. Differential regulation of neuronal transcriptome by apoE isoforms is a newly identified biological mechanism, which has both implication in the development and aging of the CNS.

Dataset Information

Small molecule structure correctors abolish detrimental effects of apolipoprotein E4 in cultured neurons.

Publications

Small molecule structure correctors abolish detrimental effects of apolipoprotein E4 in cultured neurons.

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